Lateral laser fiber for high average power and peak pulse energy

ABSTRACT

An improved optical fiber comprising a waveguide with an input for coupling focused laser energy into the waveguide and communicating electromagnetic radiation in a propagation direction to an internally reflective tip of the waveguide, a tissue contacting surface wherein the light path from the reflecting surface to the transmitting surface in substantially homogenous in refractive index and cooled by fluid flow. In minimizing the variations in refractive index within the lateral light path, while providing active cooling directly below the tissue contact surface, the invention prevents internal reflections and beam distortion and greatly improves the efficiency and durability of the laterally directing probe. Free rotation of the tissue contact surface, about the lateral tip, may be provided and tissue vaporization efficiency may be improved by providing a morcellating tool on the tissue contact surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional U.S. patent application Ser. No.11/148,817, filed Jun. 8, 2005, now U.S. Pat. No. 7,909,817, entitled“LATERAL LASER FIBER FOR HIGH AVERAGE POWER AND PEAK PULSE ENERGY,”which application is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to applications of lasers toendosurgery and specifically to delivery of high energy density or highaverage power to tissues located about body lumen, such as the prostategland about the urethra.

BACKGROUND OF THE INVENTION AND DESCRIPTION OF THE PRIOR ART

Treatment of benign prostatic hypertrophy (BPH) with laser energy has asomewhat checkered past, but in recent years advances in theunderstanding of laser-tissue interactions and laser design have enabledrealization of much of the promise of the initial concept. Thelongstanding “gold standard” for surgical treatment of benign enlargedprostate glands is a technique called TURP: Transurethral Resection ofthe Prostate. In TURP procedures, an electric current is passed throughworking tips of various shapes, heating them to permit tissue to beselectively carved or charred away. While TURP is widely used with goodclinical results, significant bleeding is common and the procedure canbe time consuming, particularly where the glands are large.Post-operative swelling of tissues remaining post-TURP requirescatheterization to permit release of urine and hospital recovery can beprotracted. Post-operative pain is often prolonged and complicationssuch as bladder neck strictures and nerve damage are relatively common,leading to a fairly high incidence of retrograde ejaculation,incontinence and temporary impotence among patients.

The VLAP procedure of the 1990s (Visual Laser Ablation of the Prostate)promised solutions to the problems with TURP, but the dominant laserwavelength (1064 nm) penetrated too deeply into the prostate tissue suchthat deep coagulation (tissue death but not removal) resulted andnon-target tissues were often damaged inadvertently. Fluid uptake inthese damaged tissues caused post-VLAP complications and it wasdifficult for surgeons to judge the actual degree of tissue death thatwould result beneath the surface treatment.

Contributing to this problem was the broad spectrum of lateral fiberfunction, with fibers manufactured by as many as two dozen companies.With no established minimum performance standards, most lateral emittingfibers of the period delivered relatively diffuse energy withsignificant scattered radiation such that tissue effects. varied widelyfrom surgery to surgery. The vast majority of urologists whoexperimented with VLAP in the 1990's, and various modifications thereof,abandoned the method and returned to TURP by about 1996.

More recently, a new technique called PVP (Photo Vaporization of theProstate) has spearheaded resurgence in applications of lasers to BPHsurgery, driven more by patients than by the Urological Specialty, forthe reportedly very low incidence of side effects. The technique uses532 nm light that is strongly absorbed by hemoglobin such that surfacevaporization of tissue is the dominant affect. In addition, the lateralfiber used in the procedure (GreenLight™, U.S. Pat. No. 5,428,699,referenced below as prior art) is more efficient than most that wereavailable in the 1990's such that high energy density spots arepresented to tissue with little damaging scatter. Also contributing tothe overall high performance of the system (laser plus fibercombination) is the inherently high energy density of the laser itself,as taught by U.S. Pat. No. 6,554,824 (Davenport, et al.). With anaverage of 80 W of 523 nm light provided to the fiber, approximately 70W is delivered laterally to the target tissue within a small diameter,substantially circular. The output spot energy profile produced is suchthat substantially all of the illuminated tissue is vaporized.

The PVP procedure is popular with patients and surgeons because it isfast, essentially painless (no prolonged, post-operative tissuesloughing), offers immediate relief (often no catheter is requiredbeyond initial recovery), generally requires no hospital stay and has avery low incidence of complications. Such surgeries should also bepopular with private and government insurers in that the overall costsassociated with treatment are considerably lower for PVP than for TURPin most cases.

While enlarged prostate glands of typical size (30 grams) may be treatedsufficiently within as little as 15 minutes with PVP, larger glandsprove problematic. As the surgery proceeds, the output “cap” of thelateral fiber degrades: the surface through which the laser light passesbecomes opaque or “frosted”, scattering light. The damage accelerateswith continued use and eventually the erosion at the surface extendscompletely through the cap and surgical irrigation fluid leaks into thecap as it heats and cools with each laser pulse.

Since the redirection of light within lateral fibers such as this isbased upon total internal reflection (TIR) due to refractive indexdifferences of the fiber core and the air trapped in the protective cap,influx of aqueous solution at a refractive index more similar to theglass than to air disrupts this condition and the fiber fails by firingaxially. Such failures can be catastrophic, with uncontrolled laseremission causing bladder neck damage or bladder or urethral perforation.As a minimum inconvenience, at least two GreenLight™ fibers may berequired for large glands resulting in delays and added surgical costs.

A competing technique is also gaining some ground: HoLAP or HolmiumLaser Ablation of the Prostate. In theory, the holmium wavelength iseven more favorable than KTP (532 nm mentioned above, or frequencydoubled Nd:YAG) for controlled tissue affect with stronger absorptionresulting in even less underlying coagulation. In addition, proceduralproblems and cost issues with the PVP can be avoided. The bright greenKTP laser emission interferes with vision requiring special endoscopecamera filters and orange safety goggles for surgical staff and thefrequency doubled, 200 W Nd:YAG laser requires non-standard electricalpower (50 A, 208 VAC) and high flow cooling water. The KTP laser iscostly (about.$80,000) and is currently a “single procedure box”,meaning only BPH surgery is done with the appliance, and GreenLight™fibers are extremely expensive for a disposable device at US $875 each.In contrast, the holmium laser is competent in treating other urologicaland non-urological conditions from kidney stones to ruptured spinaldiscs. It would be desirable to provide high performance lateral fibersat reasonable costs for holmium lasers for providing lower cost laserBPH surgery to a broader population.

In the PVP procedure, considerable effort and expense has been expendedin producing lasers (Davenport, et al.) and fiber delivery systems (Pon)that minimize irradiation of tissue with low energy density light inthat the lower energy densities may cause deep thermal damage withoutimmediate tissue removal. This is not a new observation. Beginning in1989, the author of the current art personally has experienced laserinjuries from a broad range of laser wavelengths and energy profiles andhas long noted that higher energy density injuries heal much morerapidly than low energy density injuries, with negligible collateraltissue damage, regardless of the laser wavelength. Unfortunately, inspite of the high energy density light produced by the KTP laser taughtin Davenport, the degradation in performance of the fiber taught in Ponis such that the proportion of low energy density light delivered to thetissue steadily grows as the procedure proceeds.

Holmium energy is strongly absorbed by water and is absorbed to a lesserdegree by other tissue components, including blood, so where the PVPlaser becomes less effective as surface tissue is ablated and underlyingtissue are blanched of blood, the holmium continues to work with highefficiency. Owing to the stronger absorption of the holmium laser energyby tissues, the depth of laser energy penetration for the holmium iseven lower than that for KTP, so unwanted deep tissue death has thepotential to be reduced even further, if high energy density can bereliably delivered to the target tissues over the course of theprocedure.

The barriers to holmium applications in BPH are minor but persistent.Protective cap degradation appears to be more pronounced with theholmium wavelength than with KTP, possibly due to a higher degree ofinteraction of the light with the cap material (silica), the high pulseenergy density and the considerable heat generated by interactions ofthe laser energy with the aqueous irrigation fluid and tissues. Inparticular, water attacks the hot silica through hydrothermal erosion.This is complicated (and accelerated) by devitrification of the surfacethat is catalyzed (at elevated temperatures) by ions commonly found intissues and irrigation fluids: alkali and alkaline earth metal ions suchas sodium (I) and calcium (II).

The photo-thermal and/or photo-acoustic shock waves that are generatedby the laser pulses in the glass and in the water are so intense thatcaps of similar dimensions to those used in the PVP fiber can simplyshatter to dust at average powers of 40 W or more. Thicker caps resistthis damage but remain susceptible to erosion failures in apparentexcess of that seen in PVP. (Much of the erosion problem could besurgical technique related, in both procedures, e.g. some surgeons mayhold the holmium fiber in closer proximity to tissue than KTP fibers andsome may clean the fiber tip intra-operatively while others may not.)

Further, the energy density profile of holmium lasers contains a broadermix of modes than that produced by the KTP laser used in the PVPprocedure. As taught by the author of the present art in U.S. Pat. No.6,282,349 (Griffin) and other publications, holmium lasers are notoriousfor thermal lensing problems within the lasing medium, resulting invariable mode output beam profile. This broader distribution presentsareas of the beam profile that are not of sufficient energy density tocause tissue vaporization and undesirable coagulation is the result.Reducing the high order modes produced by the laser itself by reducingthe heating that the pump energy produced in the laser medium, as taughtin Davenport, is not the sole means of minimizing this problem, nor isit the most economical or logical means. The higher order modes may beselectively excluded from coupling to the surgical fiber (modestripping), or preferably, the higher order modes may be converted tolower order modes within the energy delivery fiber, at thelaser-to-fiber coupling or at the fiber output.

The energy density profile at the fiber output surface is not onlycritical for achieving the desired tissue response, but for prolongingthe fiber performance. Energy densities presented at the fiber outputthat are insufficient for tissue vaporization promote tissue adhesionsto the fiber tip. Adhered tissues give rise to conditions that promoteacceleration of performance degradation. GreenLight™ fibers modified foruse on holmium lasers function very well in comparison to other fiberdesigns, indicating that the superior efficiency of the fiber output iscritical to clinical function.

A less efficient fiber design, the (DuoTome™), is sole holmium fiberthat is capable of delivering average holmium power equivalent to theGreenLight used with the KTP laser, but it requires a 100 W input toachieve vaporization rates similar to the GreenLight/PVP procedure. At100 W input, the DuoTome output spot presents lower energy density totissue than does the GreenLight due to more scatter and cylindrical lensdistortion within the lesser fiber design such that, even given thesuperior absorption of holmium energy by target tissues, morecoagulation results than is clinically desirable or necessary.

Inefficiency breeds excess heat at the fiber tip, which promotes tissueadhesions and fiber damage, so fibers are even more prone to prematurefailure in holmium BPH treatment than they are in PVP. Surgical progressis not quite as rapid nor are target tissues quite as precisely ablated.Further, energy density in the fiber output spot is critical tosuccessful vaporization without significant concomitant damage tocritical, non-target structures near the site of therapy.

The DuoTome™ avoids irradiating non-target tissues (with the scatteredlaser light in the output) by sheathing the cap in stainless steel. Onlya tiny window is presented for the laser energy to escape. As aconsequence of trapping the undesirable energy within the steelenclosure the fiber tip gets hot in use and hot steel can also causeunwanted tissue damage and complications. Furthermore, the stainlesssteel containment sacrifices protective cap thickness in an applicationwhere total diameter is limited by the size of the working channelprovided within the endoscopic device. The maximum diameter limit forthe smallest working channel (7.5 Fr.) in rigid cystoscope/resectoscopesis about 2.45 mm where compatibility with most flexible cystoscopes(presenting working channels as small as 6 Fr.) the maximum diameter forthe device is about 1.75 mm and the length of rigid section (typicallythe cap) should not exceed about 12 mm least the device not easily passthe channel in moderate deflection.

At least two other fiber designs have been tried with the holmiumlasers, as taught by Griffin and Brekke, referenced below. Both are highefficiency designs that utilize fiber-to-cap fusion to minimize scatter.Both fail at approximately 40 W through catastrophic disintegration. Itis thought that the residual stress concentrations in the fiber-to-capfusion region likely render the fused fibers more susceptible to thethermal shocks encountered in the surgery than non-fused fibers.

All current art lateral fibers based upon total internal reflection(TIR) at tips—polished at the critical angle as defined by Snell's Lawas opposed to external reflector designs such as U.S. Pat. No. 5,242,437(Everett)—that are designed for surgeries such as prostate resectionsuffer the opacity at output failure mode, where the glass surface incontact with tissue and/or irrigation fluid and/or bodily fluidsdegrades through hydrolysis and devitrification. Even minor degradationof the output surface quality causes difficulties in surgery. There istypically a coaxial, visible laser wavelength transmitted within theoptical fiber that serves the surgeon in orienting the fiber outputproperly on target tissues: the “aiming beam”. As the output surfacedegrades, so the clarity of the aiming beam degrades, making preciseorientation more difficult.

Accordingly, fibers are also equipped with accessory “orientationmarkers” that are typically proximal to the output area, generallyopposite the fiber output such that they may be visualized when thefiber is properly positioned, pointing generally at tissue rather thangenerally at the surgeon or endoscopic equipment. These markers areusually ink printed lines or text on transparent heat shrink tubing thatare carefully positioned with respect to the fiber output duringassembly. As the fiber continues to degrade with use, it becomes moreinefficient such that more laser energy is consumed in heating thedevice, causing more tissue adhesions, more energy absorption and moreglass degradation, i.e. the degradation progress is governed by secondorder kinetics and accelerates. As the output tip heats to greater andgreater temperatures, the thermally labile orientation marker becomesdamaged, further reducing the ability of the surgeon to properly orientthe fiber output.

Where temperatures rise even further, adhesives used to secure theprotective cap to the fiber fail, or the fibers' polymer buffer coatingsthemselves fail, and the cap may dislodge. A dislodged cap is acatastrophic failure (axial emission) and often requires prolongedexpeditions within the urinary tract for the purpose of retrieving theloose cap.

In summary, heating of glass tipped fibers in use results in multipleproblems far in excess of increasing the depth of tissue death beyondthe therapeutic necessity. Elevated temperatures greatly acceleratecatalytic devitrification of the silica dissolution surface, resultingin loss of surgical orientation. Reduced surgical efficacy and precisionresult for increasing scatter at fiber output. Adhered tissues absorbscattered laser energy and carbonize. Carbonized tissues absorb evenmore laser energy and may reach temperatures in excess of 750° C. at theprotective cap surface. Larger temperature differentials in the lowthermal conductivity silica material may produce stresses sufficient tocause fracture.

It would be desirable to address the failure modes and inefficiencies ofside fire fibers to permit use with widely deployed lasers to achieveclinical results similar to, and theoretically superior to thoseachieved with the GreenLight™/PVP procedure, as measured by clinicaloutcome and speed of surgery, with better ease of use and lower costs.It would also be desirable to improve the performance of the fiber usedin PVP and, for that matter, any surgery that is enabled or facilitatedby fibers that emit radiation lateral to the fiber axis.

Rowe (U.S. Pat. No. 5,246,436) discloses a low hydroxyl fused silicafiber optic with a metal coated tip, with an opening designed to leakenergy in a generally lateral direction that is housed in a hollow tubepossessing an opening corresponding to the location of the radiationleak through which cutting energy is to pass. The tip is irrigated byfluid transmitted by one lumen and aspirated by a second lumen.According to Rowe, because the laser energy is highly absorbed by water(the main component of the cooling fluid and the target tissue), airbubbles formed by the laser pulses at the fiber tip permitirreproducible and uncontrolled energy coupling to delicate targettissues.

The fluid flow is designed to sweep those bubbles away as they areformed, providing improved control of laser to tissue interactions. Itis unclear if the laser energy exiting the opening in the hollow tubesurrounding the fiber tip, or hot gas bubbles formed by the laser energythat are permitted brief contact with tissue, or both, are intended todo the surgical work. Regardless of the intended mechanism, laser energyand fluid are in direct communication with the target tissue in Rowe.

While not specifically addressed in Rowe, the low [OH] fused silicafiber taught is not terribly transparent to the mid-IR energy producedby the Er:YAG laser of the preferred embodiment such that, for thedevice to function at all, the entire fiber length can not be more thanseveral centimeters. The lateral tip design disclosed in Rowe is alsoinefficient as much of the laser energy that does manage to reach thelateral tip will convert to heat in multiple reflections therein. Giventhe delicate surgery addressed by the Rowe design, these inefficienciesmay well be intentional, or at least acceptable, but this does not alterthe fact that such a design could not possibly function in majorsurgery, such as prostate resection by Er:YAG infrared energy asdisclosed herein. Further, due to the encapsulated volume within whichthe Rowe device must function, it requires two fluid conduits withmetered inflow and metered aspiration of irrigation fluid to preventinflation or collapse of the eye in use.

Similarly, U.S. Pat. No. 6,802,838 (Loeb, et al.) discloses a deviceintended to be inserted “interstitially” into tissue, where net fluidflow to or from the target tissue is known to be problematic in thesurgical art. Loeb, et al. discloses a more traditional lateral emittingfiber with a bevel tip that is encapsulated to preserve the refractiveindex barrier needed to cause the light to be redirected off axis(similar to the present invention and other prior art). Loeb, et al.,also discloses the lateral fiber tip disposed within a hollow cylinderthrough which cooling fluid flows, but as in Rowe, Loeb, et al.'sprimary purpose is not to cool the fiber tip, but the tissue. Again,there are at least two independent fluid channels within the hollowcylinder with fluid flow propelled by pressure and/or aspiration andboth laser energy and irrigation fluids are in direct communication withthe target tissue through the common opening (window). As in Rowe, Loeb,et al., further discloses that hot gasses generated by the laserinteraction with tissue and irrigation fluids are swept away from thesurgical site by the fluid flow, preventing excessive heating andsuppressing unwanted, deeper coagulation (or other damage) in non-targettissue. Loeb, et al, does suggest that the fiber output may also be keptclean of contaminating tissue by the flowing fluids, but the inverse istrue. By providing access to the optical output and further, bypreferentially propelling loose tissues through that access port, theoutput surface is placed in great jeopardy of contamination by tissues.

Similarly, U.S. Pat. No. 5,496,309 (Saadat, et al.) discloses aunidirectional fluid flow system about a light-redirecting prism incommunication with the flat tip of an optical fiber. The prism isrequired to have substantially higher refractive index than the fluid tosupport reflection of energy in the lateral direction. The lightredirection bevel is not formed on the delivery fiber since the fibermaterial is not of sufficiently higher refractive index. Again, thefluid flow and laser energy are in communication with the target tissuethrough a common, open port.

The likely reason for teaching an open port through which both laserenergy and fluid flow pass or may pass, in Rowe, Loeb, et al., andSaadat, et al., is the prevailing opinion in the field that mid-infraredenergy is so strongly absorbed by water that encapsulating a fluidthrough which IR energy passes will result in structural failures due tothe expansion of rapidly vaporizing water. It is the thesis of this artthat this is not the case.

The absorption spectrum of liquid water shown in FIG. 20 clearly showswhy Rowe teaches not to contain the water within a limited volume: theabsorption coefficient of water at Er:YAG wavelengths is very large,meaning very little laser energy beyond the heat of vaporization isrequired to convert the water to steam. For Ho:YAG, however, theabsorption coefficient is more than two orders of magnitude lowermeaning the same volume of water would require more than 100-fold morelaser energy to vaporize it. It is true that a fiber delivering holmiumlaser energy into a large volume of water creates bubbles (this bubbleformation and collapse was thought to be the source of “acousticshockwaves” for breaking-up kidney stones years ago, although themechanism for holmium laser interaction with renal calculi is not knownto be photochemical and thermochemical). Proponents of PVP suggest thatthis bubble formation robs the laser beam of sufficient energy tovaporize tissues. In surgery with holmium lasers, however, the simplefact of the matter is that large bubbles are not formed when the fiberis in close contact with tissue: the path length of travel through thewater is not sufficient to absorb enough energy to change phase or suchphase change is so limited that it has minimal impact.

Loeb, et al. and Saadat, et al. miss the opportunity to protect theoptical surface of the lateral fibers by exposing them directly totissue contact, most likely for the mistaken impression that to dootherwise is folly. Simply by capturing the fluid flow within a solid,but transmissive window, failure of the art taught in Loeb, et al. andSaadat, et al. would be greatly forestalled.

The fundamental mechanism of bi-directional fluid flow disclosed byLoeb, et al. and Rowe are similar, and both are designed to addresssimilar surgical issues with respect to excess and uncontrolled heatingof tissues by steam bubbles generated by the laser interaction with theirrigation fluid and tissues. Further, the laser and irrigation fluidare in direct communication with the target tissue through a commonphysical opening in the fluid flow-supporting hollow tube, exposing thecritical optical output surface to direct contamination. The artdisclosed herein utilizes unidirectional fluid flow to cool the tissuecontact surface of the device where only laser energy is in directcommunication with the target tissue. Cooling fluids exit the devicethrough a remote port or ports formed expressly for that purpose andunidirectional flow greatly reduces the potential for tissue migrationthrough a port to the optical output surface.

Accordingly, the unique strategy disclosed herein is to decouplefunctions that need not be coupled, thereby enabling optimization ofeach design for that function alone: the optical output and tissuecontact surfaces are separated as are the laser energy and fluid outputports.

Fresnel reflections in lateral devices are a fundamental source ofinefficiency, causing unwanted heating, tissue destruction and tissueadhesion. Where the light energy exits the sidewall of a fiber andenters the wall of the protective cap a portion of the energy reflectedat each refractive index boundary. The amount of energy that isreflected is proportional to the difference in the refractive indexdifferences acts the boundary as well as the light-to-surface contactangle. As Fresnel reflections increase in intensity with off-normalcontact angles, it is desirable to minimize the angle that the worstcase ray within a fiber will impart the cylindrical fiber outer diameterand the cylindrical protective cap inner diameter. More critically, inmost prior art there are light-to-surface contact angles that exceed thecritical angle as defined by Snell's Law, angles where all of the lightwill reflect rather than just a portion thereof, similarly to thedesired 100% reflection provided by the bevel tips on the fiber termini.

Pon (U.S. Pat. No. 5,428,699) discloses a mechanism for reducingreflections within lateral devices by reducing the incident angles ofthe bulk of the light exiting the fiber cylindrical wall and enteringthe protective cap cylindrical wall to below the critical angle forreflection. This reduction may be accomplished as simply as utilizing athicker than standard glass cladding layer over the fiber core. Byproviding a larger diameter where the light exits the side of the fiber,worst-case rays exiting near the edges of the core encounter much lowerangles (relative to normal to the boundary tangent). Pon also teachesalternatives for further reductions in incident angles such as usingsquare and triangular fiber segments at the bevel tip, to provide flatexit surfaces, and forming flat surfaces upon the thickened fibercladding opposite the output.

Griffin (U.S. Pat. No. 5,562,657) and Brekke (U.S. Pat. No. 5,537,499)disclose another mechanism for reducing Fresnel reflections bysubstantially eliminating the large difference in refractive indicestraversed by the emitted rays through fusion of the beveled fiber tip tothe protective cap; through an intermediate layer of glass and directly,respectively. Griffin teaches a fused sleeve about the fiber at theoutput end, upon which composite the reflective bevel is polished. Asubsequent fusion of the sleeved and beveled tip to the protective capeffectively eliminates all reflections by eliminating the air layerbetween fiber and cap. Brekke teaches direct fusion of the fiber outputto the cap inner wall.

A further prior art design is disclosed in U.S. Pat. No. 4,740,047 (Abe,et al.). The Abe, et al. invention seeks to prevent misdirected laserenergy from damaging patient tissue by including specially arrangedreflective and antireflective coatings on the appropriate surfaces. Thereflective and anti-reflective coating layers taught by the Abe, et al.patent, however, can melt or carbonize at high temperatures during use.Where the coating layers become damaged or carbonized, the degradationand failure cascade is initiated.

Abe, et al. further teaches flat surfaces within the device, but theseflat surfaces are on the protective cap outer diameter where thecylindrical distortions are of far lesser concern than on the fiberouter diameter and cap inner diameter where the curvature is much higherand the refractive index difference in use (glass to air and air toglass) is much greater than for the outer diameter (glass to aqueoussolution). While the flat output of Abe, et al. could be construed as anattempt to reduce light to surface angles and cylindrical distortions,in that it appears on both sides of the cap it was likely intended topermit the antireflective and reflective coatings to be applied andfunction independent of angular considerations.

Further compromises to performance result from the highly curvedsurfaces through which the laser energy must pass. Beyond causingsignificant scatter within the devices, these surfaces also act aslenses and distort the output profiles, resulting in a loss of energydensity at the therapeutic site. These distortions are reduced by arttaught in Pon, Griffin and Brekke, but riot in Loeb, et al. or Abe, etal.

Prior art that utilizes fluid flow does so with flow about the outersurface that is last traversed by the laser energy and is in directcommunication with tissue. This arrangement is logical in that the fluidflows are intended to protect the tissue rather than the device. Fusionof fiber output surfaces to tissue contacting structures is used inprior art for reducing reflections (also known as scatter due to thecomplex reflection patterns involved where myriad angles and curvaturesare involved) and minimizing output spot distortions, but high residualstresses in the protective cap that can not be annealed (due to thepresence of low thermal damage polymers in the structures) make fusedfibers highly susceptible to the thermal shocks of high energy surgery,particularly pulsed holmium laser surgery.

Antireflective coatings are taught these purposes as well, but tolimited effect in actual practice. Reduced contact angles, as taught byPon, have the greatest practical effect in improving fiber performance,when carried out on the surface(s) where contact angles are highest,i.e., the fiber outer diameter and the protective cap inner diameter

SUMMARY OF THE INVENTION

The present invention provides design improvements to minimizereflections within the lateral output structure of surgical fibers,forestalling the onset of protective cap degradation and tissueadhesion, while improving the beam quality (energy density) of thelateral output profile for prolonged high performance lifetime insurgery and enabling precise direction of the vaporization of unwantedtissues without deep tissue coagulation and minimizing damage toimportant structures near the site of the therapy.

This is achieved in one embodiment by providing two separate protectivecaps that separate the functions that are in conflict in prior art: one(inner) cap for containing the gas (or vacuum) at the polished bevelsurface that maintains the necessary refractive index difference forTIR, and a second cap to absorb the abuse of direct tissue contact. Theinner cap may be just thick enough to protect the bevel tip, or thickenough to permit formation of a flat output surface without penetratingthe fiber core. Complete cap penetration in erosion will not result inaxial transmission as in all prior art in that the inner cap remains toprotect the TIR condition, i.e., the new art provides double containmentfor added safety.

Additional protection may be provided by irrigation flow between theprimary (gas containment) cap and the tissue contact cap. The fluid flowbetween the caps (intra-cap flow) serves well to cool the tissue contactcap from within and mainly serves to reduce the reflections andcylindrical distortions in the inner cap to outer cap transition by moreclosely matching the refractive index of glass. Flow is notintermittently disrupted due to intimate tissue contact and bubbleformation as it is in the prior art and flow is provided for the purposeof preventing unnecessary heating in the device, as well as somecooling, as opposed to cooling the tissue. It is the thesis of thistechnology that device efficiency is of paramount import: to reduce,forestall onset or eliminate degradation improves surgical precision andspeed, obviating the need of tissue-cooling. Further, flow does not exitthe device through a port provided for laser emission, as in prior art,since this does not accomplish the goal of keeping the primary emissionwindow clean while keeping the working surface cool.

A more interesting approach than intra-cap flow cooling, alone, is onethat uses a laminar flow (or flows) within a compound outer capstructure for more immediate cooling of the device at the tissue contactpoint, from within the working cap itself. This concept is really anextension of intra-cap flow cooling, but is a special case where the twocap surfaces are not provided by separate structures, but are affordedwithin a single, monolithic cap that provides a lumen of some typewithin to conduct coolant.

The monolithic cap with integral laminar flow channels functionsbecause, though made through laminating layers of silica material, withthermal fusion, the cap is a separate component that may be annealed toremove the stresses of fusion fabrication. It is no more susceptible tothermal shock damage than a standard cap of prior art, dry, and withsufficient fluidic flow within the regions that are subjected to rapidthermal cycling by the interaction of the laser pulses with tissues,thermal stresses are greatly reduced over prior art.

The concept can be extended ad infinitum by utilizing a laminar flow capwith intra-cap flow as described previously, and by adding more layersof laminar flow. At some point, however, one reduces the structuralintegrity of the device as more and more volume that was previouslysilica is replaced with fluid flow channels, but even multiple thin wallsilica layers, separated by fluid flow channels, may be of interest insome applications. As one silica barrier fails, flow is moreconcentrated in the damaged area by leakage through the new port formedby failure. Thin-wall failures are less likely to distort the laseroutput than thick-wall failures in that perforations through thin wallshave more similar opening diameters on the outer and inner diameters.

Device output energy densities may be increased by forming curved bevelreflection surfaces (focusing mirrors), by reducing the maximum lightpropagation angles within the base fiber and/or at the fiber tip and byproviding additional beam shaping lens surfaces at refractive indexbarriers throughout the design. A reflective metallic marker may beprovided for a thermal stable orientation mark directly opposite thefiber output in fixed cap orientation embodiments.

Free rotation of the outer protective cap is provided in one embodimentto increase the surface area of tissue to cap contact throughout thesurgery, further forestalling degradation onset, tissue adhesions andfiber failure. A scraping surface is provided on the tissue contactsurface of one embodiment for enhanced removal (mechanical) ofcoagulated tissues, accumulations of which would otherwise reducesubsequent laser energy to tissue interaction.

Fusion of the inner protective cap is possible in this invention becausethe thin-wall harbors less internal stress than thicker caps required insingle cap designs and because the thin-wall inner cap is not in contactwith vaporizing tissues, but is shielded by the thicker working cap andinsulated by either air (dry design) or fluid flows (wet designs).

“Fluid flow” embodiments of the new art also anticipate the use ofnon-aqueous fluids that offer greater transparency at the surgicalwavelength, better heat transfer and/or more attractive refractiveindices than aqueous fluids, e.g., fluorocarbon solvents. Further,materials that are not fluid or that become fluid at elevatedtemperature are also anticipated, such as amorphous fluoropolymers(e.g., DuPont Teflon AF 1600) and index matching gels.

Among the objects of the present invention are the following:

To provide a new and useful lateral fiber output termination forresistance to hydrothermal damage to energy delivery devices used insurgical procedures involving vaporization for removal of unwantedtissue;

To provide a new and useful lateral fiber output termination forresistance to devitrification damage to energy delivery devices used insurgical procedures involving vaporization for removal of unwantedtissue;

To provide a new and useful lateral fiber output termination forresistance to tissue adhesions in surgical procedures involvingvaporization for removal of unwanted tissue;

To provide a new and useful lateral fiber output termination forresistance to thermal shock damage to devices in surgical proceduresinvolving vaporization for removal of unwanted tissue;

To provide a new and useful lateral fiber output termination forresistance to photo-acoustic shockwave damage to devices in surgicalprocedures involving vaporization for removal of unwanted tissue;

To provide a new and useful lateral fiber output termination forimproved energy to target tissue coupling efficiency in surgicalprocedures involving vaporization for removal of unwanted tissue;

To provide a new and useful lateral fiber output termination forimproved energy density at target tissues in surgical proceduresinvolving vaporization for removal of unwanted tissue;

To provide a new and useful lateral fiber output termination forimproved aiming laser energy density at target tissue for enhancedorientation in surgical procedures involving vaporization for removal ofunwanted tissue;

To provide a new and useful lateral fiber output termination forimproved accessory orientation in surgical procedures involvingvaporization for removal of unwanted tissue;

To provide a new and useful lateral fiber output termination forreducing collateral tissue damage about or near target tissue insurgical procedures involving vaporization for removal of unwantedtissue;

To provide a new and useful lateral fiber output termination for reducedscatter of therapeutic energy in surgical procedures involvingvaporization for removal of unwanted tissue;

To provide a new and useful structure on lateral fiber outputterminations for enabling concomitant mechanical removal of coagulatedtissues in surgical procedures involving vaporization for removal ofunwanted tissue.

The novel features that are considered characteristic of the inventionare set forth with particularity in the appended claims. The inventionitself, however, both as to its structure and its operation togetherwith the additional objects and advantages thereof will best beunderstood from the following description of the preferred embodiment ofthe present invention. Unless specifically noted, it is intended thatthe words and phrases in the specification and claims be given theordinary and accustomed meaning to those of ordinary skill in theapplicable art or arts. If any other meaning is intended, thespecification will specifically state that a special meaning is beingapplied to a word or phrase. Likewise, the use of the words “function”or “means” in the Description of Preferred Embodiments of the inventionis not intended to indicate a desire to invoke the special provision of35 U.S.C. §112, paragraph 6 to define the invention. To the contrary, ifthe provisions of 35 U.S.C. §112, paragraph 6, are sought to be invokedto define the invention(s), the claims will specifically state thephrases “means for” or “step for” and a function, without also recitingin such phrases any structure, material, or act in support of thefunction. Even when the claims recite a “means for” or “step for”performing a function, if they also recite any structure, material oracts in support of that means of step, then the intention is not toinvoke the provisions of 35 U.S.C. §112, paragraph 6. Moreover, even ifthe provisions of 35 U.S.C. §112, paragraph 6, are invoked to define theinventions, it is intended that the inventions not be limited only tothe specific structure, material or acts that are described in thepreferred embodiments, but in addition, include any and all structures,materials or acts that perform the claimed function, along with any andall known or later-developed equivalent structures, materials or actsfor performing the claimed function.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and 1B is side view in section along the centerline of the priorart in Abe, et al., with a cross sectional view taken approximately atthe center of the output plane.

FIG. 2A and 2B is side view in section along the centerline of the priorart in Rowe, with a cross sectional view taken approximately just infront of the output plane.

FIG. 3A and 3B is side view in section along the centerline of the priorart in Loeb, et al., with a cross sectional view taken approximately atthe break in the side view in section.

FIG. 4 is side view in section along the centerline of the prior art inSaadat, et al.

FIG. 5A and 5B is side view in section along the centerline of the priorart, marketed as GreenLight™, by Laserscope Surgical SystemsIncorporated, and taught in Pon, with a cross sectional view takenapproximately at the center of the output plane.

FIG. 6 is side view in section along the centerline of the prior art,marketed as ScaterFree™ by Laser Peripherals Incorporated, and taught inBrekke.

FIG. 7 is side view in section along the centerline of the prior art,marketed as MaxLight™ by InnovaQuartz Incorporated and taught inGriffin.

FIG. 8 is side view in section along the centerline of inner capprotecting the energy conduit.

FIG. 9 is side view in section along the centerline of outer cap fortissue contact.

FIG. 10 is side view in section along the centerline the combined, dryembodiment of the invention.

FIG. 11 is side view in section along the centerline of the conceptuallysimplest of the fluid cooled embodiments of the invention.

FIG. 12A and 12B is a side view in partial section along the centerlineof a sealed, fluid cooled version of the device, with a cross sectionalview taken just distal to the output plane.

FIG. 13 is a side view in section along the centerline of one portarrangement for the optically pumped, surgical irrigation variant of thedevice.

FIG. 14 is a perspective view of one alternative for distal fluidrelease in active delivery (surgical irrigation tap) to provideadditional cooling and cleanliness for the outer diameter of the tissuecontacting cap while providing mechanical morcellation of boundcoagulated tissues below the vaporization plane.

FIG. 15A and 15B is a perspective view of an alternative for distalfluid release that provides hydraulically driven rotation of the outercap, where a rotary joint is provided.

FIGS. 16A-16C are perspective views of a laminar flow monolithicsecondary cap before fusion of two layers (16A and 16B) and after fusion(16C).

FIG. 17 is a perspective view of an alternative fluid source monolithdepicting the fluid pathway.

FIG. 18 is a side view in partial section of a double helix, crossedchannel laminate cap equipped device for maximum flow in the outercoolant plane: the preferred embodiment for dual flow cooling in thedevice.

FIG. 19 is a view of a complete preferred embodiment device with primaryand secondary cap relative rotation and cap interstitial cooling.

FIG. 20 is the absorption spectrum of water in the region of interest.

FIG. 21A and 21B is a side view in partial section along the centerlineof a beam conditioning version of the device, with a cross sectionalview taken at a distal portion.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides an improved optical fiber tip forlaterally directing a laser beam. The present invention comprises awaveguide, such as an optical fiber, having a specialized output tip.Electromagnetic radiation is coupled into the waveguide and propagatesin a propagation direction along the waveguide to the output tip (alsoknown as working tip and distal tip, the energy source end of thewaveguide being proximal), also referred to by surgeons as the “crystal”(a misnomer). The output tip includes a tissue contacting surface,preferably a substantially homogeneous transmission medium, with respectto refractive index, and a reflecting surface. The reflecting surface isdisposed at an angle off normal to the propagation axis so thatelectromagnetic radiation is internally reflected in a lateral directionrelative to the propagation direction, preferably through thesubstantially homogeneous transmitting medium toward a particular areaon the tissue contacting surface. The electromagnetic radiationpropagating in the lateral direction does not cross highly curvedbarriers of media with relatively large differences in refractive indexsuch that beam profile distortions and reflections are minimized.

According to one embodiment of the invention, the waveguide includes anoptical fiber having a beveled distal end. The distal end of the tip isbeveled at an angle relative to the propagation direction of theradiation so that substantially all the radiation is internallyreflected onto a particular area of the tissue contact surface. Thebeveled tip is fused within a thin primary capsule, item one of thelateral transmission medium, to preserve integrity of the barrier inrefractive indices between the propagation medium and air or vacuum. Theoutput surface of the thin capsule (primary cap, first cap or TIRpreserving cap) may be machined normal to, or substantially normal tothe central ray of the laterally reflected energy to minimize refractionat the capsule surface. A second, thicker capsule (tissue contact cap,working cap) is disposed about the primary capsule to perform the tissuecontact function. The inner surface of the secondary capsule may bemodified to a flat surface, substantially normal to the central ray ofthe reflected energy to minimize refractions at that surface.

According to another configuration of the invention, space between theprimary and secondary capsules is filled with a fluid of substantiallysimilar refractive index (Δη<0.2) to minimize refractions at thematerial barriers within the transmission pathway of the reflectedlight. Preferred fluids are air, water, aqueous solutions, optical gelsand fluorocarbon solvents.

A specific embodiment of the inner primary cap subassembly is depictedin FIG. 8, where the waveguide 200 is a silica core optical fiber, clad205 with fluorine doped silica and coated with fluoroacryalte orfluorourethane and buffered 245 with a thick protective polymer such aspolyamide, polyamide-imide, ethylene tetrafluoroethylene, or polyesterelastomer, equipped with a beveled tip or reflective surface 225 wherethe distal portion or working tip 220 of the waveguide 200 ishermetically fused 215 within a thin silica primary capsule 210 topreserve the refractive index of medium 235 and protect the reflectivesurface 225. The buffer polymer 245 may be surface roughened 250 topromote adhesion at a later stage of assembly and an output surface 240of the primary capsule 210 may be machined flat, to provide a planarsurface substantially normal to the axis of a central reflected ray tominimize reflections and cylindrical refraction.

A simple embodiment of the outer, tissue contacting secondary capsule255 is depicted in FIG. 9. The tissue contact function requires moresubstantial material bulk and thickness, owing to the extremetemperatures encountered in vaporizing tissues and the challengingchemical use environment presented by surgical applications. Thesecondary capsule 255 presents at least two bore diameters, a smallerbore diameter 260 and a larger bore diameter 265. The larger borediameter 265 is proximal (at the opened end) and dimensioned to acceptthe roughened fiber buffer 250 and adhesive and gently reduces at 270 tothe smaller bore 260 to facilitate loading of the optical subassembly210 depicted in FIG. 8. A slight inner chamfer 275 on the larger bore265 facilitates insertion of the roughened fiber buffer 250. Areflective metallic thin film orientation marker 285 is positionedopposite the tissue contact surface.

FIG. 10 depicts the secondary capsule 255 of FIG. 9 as installed on theoptical subassembly 210 of FIG. 8 where immobilization is provided by athin film adhesive 310. The central light ray (zero order) within thewaveguide 200 is depicted by the arrows 315 reflecting off the waveguideaxis at the bevel tip 225. A secondary buffer 300, e.g., heat shrinktubing, may be applied over the section of the polymer coated waveguide200 that is proximal to the working tip 220 to provide a smoothdimensional transition, through a secondary capsule outer chamfer 305,to a maximum device diameter. In this embodiment an optional flattenedinner surface 290 of the secondary capsule 255, which is complementaryto the output surface 240 of the primary capsule 210, is also depicted.

Total reflections and output spot distortion are greatly reduced bygeometric means alone, through the elimination of curved surfaces withinthe transmitting pathway of the reflected beam 315. Rays that are nottransmitted (reflections) generally impinge upon the metallic filmorientation marker 285 and are redirected generally in the direction ofthe target tissue or are absorbed. The transmission efficiency of thissimple embodiment is typically >95% as measured by lateral energydivided by axial energy with the lateral tip removed. At high averagepower or peak pulse energy, a gold film orientation marker 285 isdamaged by the highest peak energy in the reflected beam, producing aburn through spot diameter roughly ½ of the output beam diameter andlateral efficiency is diminished by approximately 5% as reflection ofthe energy by the metallic film 285 is diminished.

In surgical use, a secondary capsule 255 that is in contact with tissuesuffers damage, becoming frosted on the output surface beginning atapproximately 20,000 Joules to approximately 100,000 Joules, dependingupon the type of silica used and the surface quality at the tissuecontact surface as well as the intimacy of tissue contact and motionsacross tissues, the laser beam qualities (CW, pulse, pulse width,repetition rate) the type and flow rate of irrigation fluid used, thetissue type and other factors outside the control of the devicedesigner. Catastrophic failure, where the frosted output erodessufficiently to perforate the secondary capsule 255, has not beenobserved for this embodiment up to 400,000 Joules delivered at 76 Waverage power, 2120 nm. Failure of the adhesive seal 310 to excludeirrigation fluid has been observed with as little as 100,000 Joulesdelivered, but due to the presence of the primary capsule 210 thelateral emission function is preserved and performance actuallyincreases due to further reductions in reflections and refractionswithin the device provided by the closer index match of the irrigationfluid to silica with respect to air.

It was thought that the aqueous fluid between the secondary capsule 255and the primary capsule 210 would absorb sufficient infrared energy toexplosively vaporize were the secondary capsule seal 310 to fail, butthis has not been observed, even where the device is removed to air andfired (for the purpose of measuring residual lateral efficiency on apower meter). The thickness of the fluid within the reflected beamtransmission pathway is apparently too thin to absorb enough laserenergy to boil enough liquid to cause expansion sufficient to causestructural failure.

In a preferred embodiment of the invention, FIG. 11, the fiber buffer(245 in FIG. 8) is missing (removed) or is substantially thinner thanstandard and the waveguide 200 is housed within a coaxial conduit oraccessory cannula channel 320, e.g., a polymer or metallic tube that issecured to the secondary capsule 255 with solder or adhesive at theouter diameter chamfer 305. Fluid may be coupled by tapping the surgicalirrigation inlet of endoscopic equipment or by a separate source orthrough a standard “T” fitting, such as those well known in the art.Fluid is conducted through the accessory cannula 320 channel, into thesecondary cap proximal bore 265 and about the fiber subassembly, to bereleased though a distal port 330 into the surgical field. The primarycapsule 210 transmitting surface and secondary capsule receiving surface260 (inner diameter) may possess the machined flats describer earlier,(240 and 290 in FIGS. 8 and 10, respectively), but owing to the closerrefractive index match of the irrigation fluid to the silica structures,such geometric mechanisms for reducing refraction and reflection are notstrictly necessary.

Another potential embodiment is the sealed coolant system depicted inFIG. 12 a and FIG. 12 b. The cooling fluid need not be aqueous in thisembodiment but may be a fluorocarbon heat transferring fluid or otherliquid. A fluid reservoir is provided within the device, depicted asmachined within the secondary capsule 255 bore at 350, but a reservoirwithin an auxiliary cannula, proximal to the lateral assembly, wouldalso function. In the depicted embodiment, the output surface of theprimary capsule 210 cap is machined flat 240 but less for geometricreduction of reflection and refraction than for producing a directional,heat driven fluidic flow. The original primary capsule 210 surface ispreserved 360 for some portion of the cap length on the output side toserve as a flow restrictor. The opposite side of the inner cap is alsomachined flat 242, but along the entire cap length to provide a freefluid flow channel. As in FIG. 10, the fiber buffer 245 forms theprimary seal between the surgical environment and the interstitial spacebetween the primary and secondary capsules, 210 and 255. As tissue isvaporized, the tissue contacting surface 252 of the secondary capsule255 heats and the heat is conducted through the thickness of thesecondary capsule to the fluid in the transmitting pathway of thereflected beam (closely spaced arrows). The interstitial fluid expandsand preferentially advances distally, away from the flow restriction360, around the tip of the primary capsule 210 to the fluid reservoir350, where it cools and replenishes flow through the restriction 360,i.e., a cyclic coolant circuit is established as depicted by the arrows.

Another embodiment for providing interstitial cooling may be provided asdepicted in FIG. 13, where surgical irrigation fluid from around thefiber in the use environment is drawn in through proximal ports 375 inthe secondary capsule 255 and exhausted through distal ports 385surrounding the lateral transmission pathway 380. This embodiment is aclose simulation of the leaking fibers that were referenced above.

Regardless of the laser wavelength used in vaporization, some tissuebeneath the vaporization plane is killed but not removed. The term ofart for this affect of laser energy on tissue is coagulation. Coagulatedtissues present far different absorption characteristics with respect tolive tissues such that the initial, highly efficient vaporization passis typically followed by a somewhat less efficient second pass, which isfollowed by a third pass at possibly lower efficiency, ad infinitum,because less efficient absorption of the laser energy leads to lessvaporization and more underlying coagulation. The decrease invaporization efficiency is not self-accelerating, but progressesmodestly as approximated by first order kinetics.

FIG. 14 depicts an alternative embodiment designed to mediate thisproblem: a distal port arrangement 395 whereby the exiting coolant ismade to pass over surfaces that are prone to contamination by tissuesand that become labile to damage where such contamination adheres. Thisembodiment is also equipped with a scraping device 390 for tissuemorcellation concomitant with vaporization. To prevent build-up oftissues within the scraper, adjacent to the laser output surface (“laseoutput”) on the outer cap, a port 395 is provided to constantly flushthe scraper and the lase output, keeping them clean.

All lase outputs of silica capped fibers degrade in time, limiting theuseful lifetime. Many of the variables that affect the onset andacceleration of the degradation are outside the control of the devicedesign, as mentioned earlier. For surgical cases and applications whereprotracted capsule to tissue contact is required, with little or slowmotion (fiber output relative to tissue), even the best possible fiberdesign will degrade and may become useless before the surgical goals arerealized, necessitating the use of a second, fresh fiber for completionof the surgery. One strategy to avoid this is to provide the device inFIG. 11 with a turning mechanism at the proximal end of the fluidconduit cannula, outside the body and endoscopic channel port. A deviceas simple as an indexing holder 620, 630 and 640, depicted in FIG. 19enables rotation of the secondary capsule 255 relative to the primarycapsule 210 to be accomplished from outside the body, via the fluidconducting conduit 670, while the fiber remains positioned in thesurgical field. Laser energy is coupled at 600, propagates distallyalong the waveguide 200 that is affixed to the proximal half of therotating device 630 at 620, passes freely through the second half of therotating device 640 to which the fluid conduit 670 is affixed, to theworking tip as described elsewhere. Fluid is supplied by a Luer 680 orother connector within the rotation device or via ports within thecannula 670 just inside the fluid seal of the working channel port ofthe endoscope.

Alternatively, given the presence of fluid flow in the device, exhaustports 410 in the secondary capsule 255 may be arranged to function asjets, imparting rotational motion to the cap when it is not in tissuecontact (or preferably, if forceful enough, even during tissue contact).FIG. 15 depicts such a concept where a rotating joint 400 is providedbetween the fluid transport cannula 320 and the outer secondary capsulechamfer 305 and a second point of centering is provided by a bulge 405in the primary capsule 210, captured with a restriction in the outer capbore 415 and equipped with exhaust ports 410 to insure that dynamic flowcushions the fiber rotation.

To insure continuous rotational motion, even in tissue contact, thefluid conduit cannula 320 can be equipped with a drive system proximalto the deepest point of endoscopic penetration, e.g., about 18′ to 24′from the working tip. This drive system is preferably hydraulic drivefrom fluid flows, if adequate to the task. Alternatively, low cost, lowvoltage electric motors and gear drives can be assembled into arelatively small accessory handle on the fiber assembly, akin to thedisposable electric tooth brushes now available: both continuousrotation and waggle about some portion of the full circle would be ofbenefit in reducing tissue adhesion problems and in spreading the damageacross a larger secondary capsule 255 surface area.

Other embodiments of the secondary capsule 255 may take myriad forms,such as that depicted as nesting components (A & B, cap with channelcircuit and sleeve, respectively) and as the final tissue contact capassembly, C, in FIG. 16. Beginning near the proximal chamfer 305, agroove 440 is machined in the surface of the cap inner structure A,extending distally to the transmission pathway, where it expands to aplane 430 encompassing enough area to cover the entire beam path. Afluid access port 450 is drilled through the cap wall to the innerdiameter and an exhaust groove conduit 425 is machined about thecircumference to the opposite side of the cap. A thin wall silica sleeveB is equipped with an exhaust port at 435 and positioned on cap A suchthat the exhaust port 435 aligns with the circumferential fluid conduit425. The two pieces are fused to form a monolithic cap C with internalfluid conduits. When assembled onto an optical subassembly FIG. 8 asdepicted in FIG. 17, the composite cap 455 substituting for thetissue-contacting cap 255 depicted in FIG. 11, the alternative inletport 475, formed on the proximal chamfer 305 of the composite cap,permits a portion of the fluid flow to be directed just below thetissue-contacting surface for additional cooling.

Further, the production of additional refractive index transitions,albeit-minor, does offer the potential for adding some additional beamconditioning optical surfaces to the structure, e.g., a meniscus-likelens penetrating the planar fluid conduit within the transmissionpathway will reduce the divergence of the output slightly as depicted inFIG. 21 for such a lens 700 formed on the inner wall 290 of a standardtissue contacting cap 255.

FIG. 18 depicts a version of the assembly with integral cooling channelsthat are simple to fabricate and represents a preferred embodiment ofthe device. Helical grooves 530 are machined in the outer diameter ofthe inner portion of the composite secondary capsule 455, for exampleunder indexed rotation with a CO₂ laser. As the grooves 530 near thedistal end of the secondary capsule 455, at about the area of beampassage, rotation is ceased to form a flat 580 on one side of thesecondary capsule 455 inner structure's outer diameter. The indexdirection is reversed until the beam approaches the beginning of thehelix, where rotation is once again begun (same direction of rotation),forming a second helical pathway overlapping the first that results inwhat has been called a “diamond” pattern (for the diamond shaped islandsof residual glass at initial diameter). Fluid access ports 520 aredrilled at the proximal extremes of the helices and the inner structureis again sleeved with a thin walled silica cylinder 550 to form asemi-laminar channel about the entire circumference of the cap that issupported by the diamond shaped islands of silica, fused to the outersleeve 550 and about the planar channel at the beam pathway. The cap isthen melted to almost seal the distal end, forming the port forinterstitial cooling flow outlet 610. A tissue morcellating blade 600 ismachined just proximal to the cap tip and distal to the beam path andthe laminar cap flow outlet port 590 is drilled through the bladesurface to the distal portion of the planar laminar conduit.

The optical subassembly 210 as depicted in FIG. 8 is inserted within thecomposite secondary capsule 455 thus formed, with the TIR bevel 570oriented to place the beam path directly in the center of the planarlaminar fluid conduit. A polymer cannula is affixed to the proximal capchamfer 540 with adhesive. Fluid provided within the polymer conduit 500couples to the interstitial space between the inner cap and outer cap aslaminar flow within the composite outer cap, as depicted by the arrows.A gold film reflector and orientation marker may be provided as depictedin earlier figures.

Further control of the output quality of the device may be provided byincorporating other art within the design, such as TIR bevel surfaceswith a slight curvature, for focusing the output beam onto tissues.Other aspects and advantages of the present invention can be seen uponreview of the figures, the detailed description, and the claims whichfollow. The preferred embodiment of the invention is described above inthe Description of Preferred Embodiments. While these descriptionsdirectly describe the above embodiments, it is understood that thoseskilled in the art may conceive modifications and/or variations to thespecific embodiments shown and described herein. Any such modificationsor variations that fall within the purview of this description areintended to be included therein as well. Unless specifically noted, itis the intention of the inventors that the words and phrases in thespecification and claims be given the ordinary and accustomed meaningsto those of ordinary skill in the applicable art(s). The foregoingdescription of a preferred embodiment and best mode of the inventionknown to the applicant at the time of filing the application has beenpresented and is intended for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise form disclosed, and many modifications andvariations are possible in the light of the above teachings. Theembodiment was chosen and described in order to best explain theprinciples of the invention and its practical application and to enableothers skilled in the art to best utilize the invention in variousembodiments and with various modifications as are suited to theparticular use contemplated.

What is claimed is:
 1. An apparatus for communicating and laterallydirecting electromagnetic radiation, comprising: a waveguide forcommunicating electromagnetic radiation, the waveguide having a distaltip with a bevel for redirecting the electromagnetic radiation in alateral direction; a primary capsule that is attached over the distaltip of the waveguide, said primary capsule further comprising a flatoptical transmission surface; and a secondary capsule that is attachedover the primary capsule and distal tip combination, said secondarycapsule further comprising a flat surface on an inner diameter thatsubstantially matches the flat optical transmission surface of theprimary capsule.
 2. The apparatus according to claim 1 wherein thesecondary capsule further comprises a secondary capsule cooling channel,said channel having a fluid input port and a fluid output port.
 3. Theapparatus according to claim 2 wherein the secondary capsule coolingchannel is helically wound within the secondary capsule.
 4. Theapparatus according to claim 2 wherein the secondary capsule coolingchannel is helically wound and counter wound, thus forming a diamondpattern, within the secondary capsule.
 5. The apparatus according toclaim 4 wherein the secondary capsule further includes a cellmorcellation blade located adjacent the flow output port of thesecondary capsule cooling channel.